Membrane oxygenators are currently in use in heart-lung machines for maintaining the respiration and blood flow of the patient during open heart surgery and the like.
It is also known to provide an integral heat exchanger to blood oxygenators to provide appropriate temperature control to the blood being oxygenated, for example as illustrated in U.S. Pat. No. 3,998,593.
In diffusion systems for blood, such as oxygenators, it is desirable for the pressure drop in the blood flow path from the beginning to the end of the system to be a minimum. However, it is also desirable for the mixing and flow characteristics of the blood to be good, for optimum oxygenation and heat exchange characteristics.
Also, particularly in membrane oxygenation, it is most desirable to provide a highly efficient means for removing gas bubbles from the blood prior to readministration to the patient. Gas bubbles may appear in the blood due to the dislodging of air bubbles trapped within the blood flow path after priming of the device, or they may enter into the blood flow line through the venous line during operation, which can be a fairly common occurence. Also, particularly in the case where porous hydrophobic oxygenation membranes are used, a highly effective bubble removing function in the apparatus serves as a final protection of the patient against bubbles coming through the pores of the oxygenation membrane, due to an increase in pressure on the gas side of the membrane, although other commercially available safety features may also be provided in this type of system.
In accordance with this invention, an integrated diffusion system for blood, specifically an oxygenation system, is provided, which may exhibit a low pressure drop, coupled with highly effective oxygenation and heat exchange, indicative of good mixing of the blood. As a further advantage, the reservoir included in the system provides a highly effective bubble trap, which is capable of removing large quantities of gas bubbles which might overwhelm other types of bubble traps which have been previously used in membrane oxygenation.